arXiv subjects

Ho-Yeon Won

Publications and source records attributed to Ho-Yeon Won.

17 recordsLinked to original sources

arXiv2026

Relativistic spatial distributions of transverse angular momentum

In our previous work [C. Lorc\'e et al., Phys. Lett. B 868 (2025) 139792], we investigated the 2D spatial distributions of transverse total angular momentum, including orbital angular momentum and intrinsic spin, relative to the canonical center (or center of spin). In the present work, we extend this analysis in two directions. First, we study the corresponding transverse boost distributions relative to the canonical center. Second, since the definition of generalized angular momentum density depends crucially on the choice of pivot, we analyze how the spatial distributions of transverse total angular momentum and boost are modified when they are defined relative to different relativistic centers, viz.~the relativistic centers of mass, energy, and spin. Considering spin-1/2 targets, we derive the corresponding 2D spatial distributions in the transverse plane, and further investigate how the spatial patterns evolve under longitudinal Lorentz boosts. Additionally, we provide the corresponding light-front distributions in the transverse plane, establishing a clear connection between the instant-form and light-front descriptions of transverse angular momentum and boost.

hep-ph↗

arXiv2026

Flavor decomposition of the gravitational form factors and mechanical structure of the proton

We review in the present talk a series of recent works on the flavor decomposition of the gravitational form factors of the proton and its mechanical properties within the framework of the chiral quark-soliton model. Starting from the energy-momentum tensor operator derived from the QCD instanton vacuum, we carry out the twist projection of the energy-momentum tensor operator into its twist-2 and twist-4 components, which enables us to isolate the $\overline{c}$ form factor originating from the twist-4 operator. We present the flavor-decomposed mass, spin, pressure, and shear-force distributions of the proton, together with the corresponding form factors. While the up quark dominates both the mass and the spin of the proton, the strange quark is found to contribute sizably to the $D$-term form factor. We also discuss the mechanical stability of the proton governed by the pressure and shear-force distributions.

hep-ph↗

arXiv2026

Transverse energy-momentum tensor distributions in polarized nucleons

We complete our study of the relativistic spatial distributions of the energy-momentum tensor inside polarized nucleons within the quantum phase-space formalism. In the present work, we focus on the components of the energy-momentum tensor involving at least one transverse index. We also explore the multipole structure of the transverse distributions in a moving nucleon. In the infinite-momentum frame, we show that the formalism reproduces the standard light-front distributions, including those with a ``bad'' component, and explains the origin of their structure.

hep-ph↗

arXiv2026

Multipole structure of the nucleon tensor form factors

We investigate the multipole structure of the nucleon tensor form factors within the chiral quark-soliton model based on the $1/N_c$ expansion. Extending the previous leading-order analysis~\cite{Ghim:2025gqo}, we include the rotational $1/N_c$ corrections. These corrections provide the leading nonvanishing contributions to the flavor components that are absent at leading order, thereby completing the flavor decomposition of the tensor multipole form factors at the present order. We numerically evaluate the isoscalar tensor charge, the isovector anomalous tensor magnetic moment, and the isoscalar tensor quadrupole moment, obtaining $g_T^{u+d}=0.81$, $κ_T^{u-d}=1.97$, and $E_T^{u+d}(0)=5.98$, respectively. The isoscalar tensor charge and quadrupole moment are mainly governed by the valence-quark contribution, whereas the isovector anomalous tensor magnetic moment receives a sizable Dirac-sea contribution. We also examine the momentum-transfer dependence of the corresponding form factors. They decrease monotonically with increasing $-t$. In particular, the isovector anomalous tensor magnetic form factor shows a pronounced falloff in the small-$|t|$ region, reflecting the importance of the Dirac sea in the tensor dipole structure.

hep-ph↗

arXiv2026

Quark orbital angular momentum as a chiral magnetic effect

The flavor-nonsinglet ($u - d$) quark angular momentum (AM) in the proton is computed based on the effective spin-flavor dynamics emerging from chiral symmetry breaking by QCD instantons. The QCD AM operators are converted to effective spin-flavor operators expressing instanton-induced chiral interactions. A large negative orbital AM $L_{u - d}$ arises as a ``chiral magnetic effect'' of the interaction of the quarks with the chiral mean field in the proton in the large-$N_c$ limit. It cancels part of the large positive spin AM $S_{u-d}$ and reduces the total AM $J_{u-d} = L_{u-d} + S_{u-d}$, in agreement with lattice QCD calculations.

hep-ph↗

arXiv2025

Mapping the transverse spin sum rule in position space

We discuss in detail the relativistic spatial distribution of transverse angular momentum, including both orbital and intrinsic spin contributions. Using the quantum phase-space formalism, we begin with the definition of the three-dimensional spatial distributions of transverse orbital angular momentum and intrinsic spin in a generic Lorentz frame. By integrating these three-dimensional spatial distributions over the longitudinal axis, we derive for the first time the relativistic spatial distributions of transverse orbital angular momentum, intrinsic spin, and total angular momentum for spin-0 and spin-1/2 targets in the transverse plane. We verify the transverse spin sum rule about the relativistic center of spin for spin-0 and spin-1/2 systems, and find that the transverse total angular momentum distribution is non-trivial, even for spin-0 targets. We also show how the distributions of transverse orbital angular momentum, intrinsic spin, and total angular momentum change with the target momentum.

hep-ph↗

arXiv2025

Relativistic energy-momentum tensor distributions in a polarized nucleon

We study in detail the relativistic distributions of energy, longitudinal momentum, longitudinal energy flux, and longitudinal thrust inside nucleons based on the quantum phase-space formalism. Similar to recent studies on the electromagnetic current, we include the effects of the nucleon polarization and show that the latter are essential for understanding how the Breit frame distributions transform under a longitudinal Lorentz boost. We also explicitly demonstrate that, in the infinite-momentum frame, these distributions allow one to recover not only the ``good'' but also the ``bad'' components of the light-front energy-momentum tensor distributions.

hep-ph↗

arXiv2025

Gravitational form factors of the nucleon and their mechanical structure: Twist-2 case

We present a series of recent works on the gravitational form factors (GFFs) of the nucleon within a pion mean-field approach, which is also called the chiral quark-soliton model. We investigate the flavor structure of the mass, angular momentum, and $D$-term form factors of the nucleon. The main findings of the present work are given as follows: the contribution of the strange quark is rather small for the mass and angular momentum form factors, it plays an essential role in the $D$-term form factors. It indicates that the $D$-term form factor is sensitive to the outer part of the nucleon. The flavor blindness, i.e, $D^{u-d}\simeq 0$, is valid only if the strange quark is considered. We also discuss the effects of twist-4 operators. Though the gluonic contributions are suppressed by the packing fraction of the instanton vacuum in the twist-2 case, contributions from twist-4 operators are significant.

hep-ph↗

arXiv2025

Nucleon tensor form factors at large $N_{c}$

We investigate nucleon tensor form factors in the large-$N_{c}$ limit. In this picture, the nucleon emerges as a state of the $N_c$ valence quarks, which were bound by pion mean fields that were created by the presence of the valence quarks self-consistently. We find that the tensor charge ($g^{u-d}_{T}=0.99$) and the anomalous tensor magnetic moment ($κ^{u+d}_{T}=7.61$) are dominated by valence quarks, while the tensor quadrupole moment ($Q^{u-d}_{T}=-7.02$) shows significant sea quark effects. We examine how these quantities vary as the average size of the pion mean field is changed, showing interpolation between non-relativistic quark and Skyrme limits. We also observe that $g^{u-d}_{T}$ and $κ^{u+d}_{T}$ depend weakly on the pion mass. In contrast, $Q^{u-d}_{T}$ exhibits strong enhancement near the chiral limit. The numerical results are in good agreement with available lattice QCD data and provide predictions for unmeasured quantities.

hep-ph↗

arXiv2024

Complete definition of $N \rightarrow Δ$ transition generalized parton distributions

We revisit the definition of the leading-twist chiral-even generalized parton distributions (GPDs) for $N \to Δ$ baryon transitions. We identify and address deficiencies in previous definitions of the transition GPDs inspired by the transition form factors of the vector and axial-vector currents. Through systematic analysis of all possible covariant structures, respecting discrete symmetries and the baryon spinor equations of motion, we derive complete sets of independent structures for the transition matrix elements of the vector and axial-vector partonic operators. They contain additional structures proportional to the light-cone vector, corresponding to transition GPDs of vanishing first moment, which were not included in previous parametrizations. Their presence is confirmed independently by the light-front multipole expansion and the cross-channel SO(3) partial-wave analysis of the transition matrix elements. Our analysis provides a complete definition of the $N \to Δ$ transition GPDs for use in theoretical and phenomenological studies.

hep-ph↗

arXiv2024

Mechanical structure of the nucleon and the baryon octet: Twist-2 case

We investigate the gravitational form factors (GFFs) of the nucleon and the baryon octet, decomposed into their flavor components, utilizing a pion mean-field approach grounded in the large $N_c$ limit of Quantum Chromodynamics (QCD). Our focus is on the contributions from the twist-2 operators to the flavor-triplet and octet GFFs, and we decompose the mass, angular momentum, and $D$-term form factors of the nucleon into their respective flavors. The strange quark contributions are found to be relatively mild for the mass and angular momentum form factors, while providing significant corrections to the $D$-term form factor. In the course of examining the flavor decomposition of the GFFs, we uncover that the effects of twist-4 operators play a crucial role. While the gluonic contributions are suppressed by the packing fraction of the instanton vacuum in the twist-2 case, contributions from twist-4 operators are of order unity, necessitating its explicit consideration.

hep-ph↗

arXiv2024

Spin-orbit correlations in the nucleon in the large-$N_{c}$ limit

We study the twist-3 spin-orbit correlations of quarks described by the nucleon matrix elements of the parity-odd rank-2 tensor QCD operator (the parity-odd partner of the QCD energy-momentum tensor). Our treatment is based on the effective dynamics emerging from the spontaneous breaking of chiral symmetry and the mean-field picture of the nucleon in the large-$N_c$ limit. The twist-3 QCD operators are converted to effective operators, in which the QCD interactions are replaced by spin-flavor-dependent chiral interactions of the quarks with the pion field. We compute the nucleon matrix elements of the twist-3 effective operators and discuss the role of the chiral interactions in the spin-orbit correlations. We derive the first-quantized representation in the mean-field picture and develop a quantum-mechanical interpretation. The chiral interactions give rise to new spin-orbit couplings and qualitatively change the correlations compared to the quark model picture. We also derive the twist-3 matrix elements in the topological soliton picture where the quarks are integrated out (skyrmion). The methods used here can be extended to other QCD operators describing higher-twist nucleon structure and generalized parton distributions.

hep-ph↗

arXiv2024

Flavor structure of the energy-momentum tensor form factors of the proton

The energy-momentum tensor form factors furnish information on the mechanics of the proton. It is essential to compute the generalized isovector-vector form factors to examine the flavor structure of the energy-momentum tensor form factors. The flavor-decomposed form factors reveal the internal structure of the proton. The up quark dominates over the down quark for the mass and spin of the proton, whereas the down quark takes over the up quark for the $D$-term form factor. We investigate for the first time the isovector $\bar{c}(t)$ form factor of the proton and its physical implications. The flavor-decomposed $\bar{c}(t)$ form factors of the proton unveil how the up-quark contribution is exactly canceled by the down-quark contribution inside a proton within the framework of the pion mean-field approach. While the proton $\bar{c}(t)$ form factor does not contribute to the proton mass, its flavor structure sheds light on how the strong force fields due to the $\bar{c}(t)$ form factor characterize the stability of the proton.

hep-ph↗

arXiv2023

Role of strange quarks in the $D$-term and cosmological constant term of the proton

We investigate the mechanics of the proton by examining the flavor-decomposed proton cosmological constants and generalized vector form factors. The interplay of up, down, and strange quarks within the proton is explored, shedding light on its internal structure. The contributions of strange quarks play a crucial role in the $D$-term and cosmological constants. We find that the flavor blindness of the isovector $D$-term form factor is only valid in flavor SU(3) symmetry.

hep-ph↗

arXiv2023

QCD angular momentum in $N \rightarrow Δ$ transitions

$N \rightarrow Δ$ transitions offer new possibilities for exploring the isovector component of the QCD quark angular momentum (AM) operator causing the $J^{u - d}$ flavor asymmetry in the nucleon. We extend the concept of QCD AM to transitions between baryon states, using light-front densities of the energy-momentum tensor in transversely localized states. We calculate the $N \rightarrow Δ$ transition AM in the $1/N_c$ expansion, connect it with the $J^{u - d}$ flavor asymmetry in the nucleon, and estimate the values using lattice QCD results. In the same setup we connect the transition AM to the transition GPDs sampled in hard exclusive electroproduction processes with $N \rightarrow Δ$ transitions, enabling experimental study of the transition AM.

hep-ph↗

arXiv2022

Gravitational form factors of the baryon octet with flavor SU(3) symmetry breaking

We investigate the gravitational form factors of the baryon octet within the framework of the SU(3) chiral quark-soliton model, considering the effects of flavor SU(3) symmetry breaking, and the corresponding energy-momentum tensor distributions. We examine the effects of flavor SU(3) symmetry breaking to the mass, angular momentum, pressure, and shear force distributions of the baryon octet. We first find that a heavier baryon is energetically more compact than a lighter one. For the spin distributions of the baryon octet, they are properly normalized to their spins and are decomposed into the flavor-singlet axial charge and the orbital angular momentum even when the flavor SU(3) symmetry is broken. While the effects of the flavor SU(3) symmetry breaking differently contribute to the angular momentum distributions for the octet baryons, they are found to be rather small. The spin and orbital angular momentum almost equally contribute to the angular momentum distributions for the octet baryons. We also estimate the effects of the flavor SU(3) symmetry breaking to the pressure and shear force distributions. Interestingly, even if we include the effects of the SU(3) flavor symmetry breaking, the shear force distributions are kept to be positive over $r$. It indicates that the Polyakov & Schweitzer local stability condition is kept to be intact with the flavor SU(3) symmetry broken. Lastly, we discuss how much the gravitational form factors vary with the effects of flavor SU(3) symmetry breaking considered.

hep-ph↗

arXiv2021

Singly heavy baryons in nuclear matter from an SU(3) chiral soliton model

We investigate how the masses of the singly heavy baryons undergo changes in nuclear matter, based on a medium-modified SU(3) chiral soliton model. Having explained the bulk properties of nuclear matter, we discuss the masses of the singly heavy baryons in nuclear matter. We generalize the vector-meson Lagrangian including the heavy-meson soliton interaction. The mass spectrum of the singly heavy baryon are obtained with the effects of explicit SU(3) symmetry breaking considered as a perturbation. The results show that the mass of the singly heavy baryon mass in nuclear medium is rather sensitive to the medium modifications of the heavy meson mass.

nucl-th↗